drm/radeon: use kobj_to_dev()

Use kobj_to_dev() instead of open-coding it.
Signed-off-by: NGeliang Tang <geliangtang@163.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/radeon/radeon_pm.c

@@ -713,7 +713,7 @@ static struct attribute *hwmon_attributes[] = {
 static umode_t hwmon_attributes_visible(struct kobject *kobj,
 					struct attribute *attr, int index)
 {
-	struct device *dev = container_of(kobj, struct device, kobj);
+	struct device *dev = kobj_to_dev(kobj);
 	struct radeon_device *rdev = dev_get_drvdata(dev);
 	umode_t effective_mode = attr->mode;